Apparatuses and methods for treating a silicon film

ABSTRACT

A method of treating a silicon film on a substrate. A silicon film is provided. The silicon film is thinned using a gas cluster ion beam (GCIB) process. The silicon film surface then is smoothed out using an etching process or an annealing process. Optionally, an encapsulation film is formed on the silicon film after the GCIB process and the etching process or the annealing process.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to treating a silicon film and morespecifically to methods and apparatuses for thinning and smoothing asilicon film.

[0003] 2. Discussion of Related Art

[0004] During the past several years, demand for silicon on insulator(SOI) substrates has greatly increased. Devices such as transistors andcapacitors typically formed on a silicon wafer can be formed on the SOTsubstrates. SOI substrates are in high demand because they have lowcurrent leakage, which allows electronic devices created on the SOIsubstrates to consume less power. Additionally, the electronic devicescreated on the SOI substrates can be made smaller.

[0005] An SOI substrate can be created using several processes. Forexample, an SOI substrate may be fabricated using a separation byimplant oxygen (SIMOX) process, of bond and etch back (BE) process, ahydrogen implant and release silicon process (sometimes known asSmartCut®) (“SmartCut®” is a registered trademark of Soitec Silicon oninsulator technology S.A.), or by using a plasma implanting oxygen intosilicon process. All of these methods are well practiced in the arts.Most of the methods of fabricating SOI substrates have some commondisadvantages, non-uniform thickness and non-smooth surface. The SOIsubstrates thus exhibit higher surface roughness than bulk or epitaxialsilicon wafers. Conventional methods to treat the surfaces of the SOIwafers include plasma polishing, chemical mechanical polishing, gascluster ion beam (GCIB) processing, annealing processing, andhydrochloric acid etching processing.

[0006] Conventional methods have several disadvantages. Plasma polishingintroduces non-uniformity and some surface damages associated withsubstrate with chemical mechanical polishing. GCIB process gives goodthickness control but a film processed under a GCIB process does nothave a very smooth surface. Annealing and hydrochloric acid etchingprocesses give good smoothness control but do not etch a filmefficiently. For example, an annealing process typically only smoothes asurface. A hydrochloric acid etching process may etch and smooth a filmbut does not have good thickness control. None of these methods canproduce thin SOI substrates that have uniform thickness and smoothsurfaces.

[0007] It is desirable to be able to fabricate a thin silicon film witha controlled uniform thickness profile and a smooth surface.

SUMMARY OF THE INVENTION

[0008] The present invention relates to methods and apparatuses fortreating a silicon film. In one aspect of the invention, to treat thesilicon film, a combination of a gas cluster ion beam (GCIB) etchingprocess and a smoothing process is used. The GCIB etching process isused to thin the film to a thickness. The smoothing process is used tosmooth the silicon film. The smoothing process can be an annealingprocess or an H₂:HCl etching process.

[0009] In another aspect of the invention, the initial non-uniformity onthe silicon film surface is mapped to obtain an initial non-uniformitymapping information. Next, a gas cluster ion beam (GCIB) is directedtowards the silicon film surface. The GCIB is modulated as the GCIB isbeing directed at the silicon film surface in accordance to the initialnon-uniformity mapping information to thin the silicon film to athickness. The silicon film surface is then smoothed using an annealingprocess such as a rapid thermal annealing. Optionally, an encapsulationfilm is formed over the silicon film that is thinned and smoothed bysoaking the silicon film with an ozone gas.

[0010] In another aspect of the invention, the initial non-uniformity onthe silicon film surface is mapped to obtain an initial non-uniformitymapping information. Next, an intended non-uniformity mappinginformation is created which is used to incorporate an intendednon-uniformity profile into the silicon film surface. Then, a gascluster ion beam (GCIB) is directed towards the silicon film surface.The GCIB is modulated as the GCIB is being directed at the silicon filmsurface in accordance to the initial non-uniformity mapping informationand the intended non-uniformity mapping information to thin the siliconfilm to a thickness and to incorporate the intended non-uniformityprofile into the silicon film surface as the silicon film is beingthinned. The silicon film surface is then smoothed using a smoothingprocess that has smoothing profile that compensates for the intendednon-uniformity to smooth out the intended non-uniformity profile such asan H₂:HCl etching process. Optionally, an encapsulation film is formedover the silicon film that is thinned and smoothed by soaking thesilicon film with an ozone gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention is illustrated by way of example and notlimitation the figures of the accompanying drawings, in which likereferences indicate similar elements and in which:

[0012]FIG. 1A illustrates an exemplary method of using a GCIB and anH₂:HCl etching processes to treat the silicon film;

[0013]FIG. 1B illustrates another exemplary method of using a GCIB andan H₂:HCl etching processes to treat the silicon film;

[0014]FIG. 1C illustrates an exemplary method of using a GCIB and anannealing processes to treat the silicon film;

[0015]FIG. 1D illustrates another exemplary method of using a GCIB andan annealing processes to treat the silicon film;

[0016]FIG. 2A illustrates an exemplary method of thinning the siliconfilm and incorporating an intended non-uniformity profile using a GCIBprocess;

[0017]FIG. 2B illustrates an exemplary method of smoothing the siliconfilm surface;

[0018]FIG. 2C illustrates an exemplary method of thinning the siliconfilm with a GCIB process and then annealing the silicon film;

[0019]FIG. 3 illustrates an exemplary gas cluster ion beam (GCIB)processing apparatus which can be utilized to thin a silicon film inaccordance with the present invention;

[0020]FIG. 4 illustrates an exemplary apparatus which can be utilized tosmooth a silicon film in accordance with the present invention;

[0021]FIG. 5A illustrates an exemplary cluster tool which can be usedfor some exemplary embodiments of the present invention;

[0022]FIG. 5B illustrates an exemplary loadlock apparatus which can beutilized to form an encapsulation film;

[0023] FIGS. 6A-6K illustrate an exemplary process of making an SOIsubstrate in accordance with the present invention; and

[0024]FIG. 7 illustrates an exemplary contour map that indicates aninitial non-uniformity profile of a silicon film.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0025] The present invention describes methods and apparatuses fortreating a silicon film, which is useful for fabricating asilicon-on-insulator (SOI) substrate. In the following descriptionnumerous specific details are set forth in order to provide a throughunderstanding of the present invention. One skilled in the art willappreciate that these specific details are not necessary in order topractice the present invention. In other instances, well known equipmentfeatures and processes have not been set forth in detail in order to notunnecessarily obscure the present invention.

[0026] The exemplary embodiments of the present invention includemethods and apparatuses for treating a silicon film. Treating thesilicon film includes first thinning the silicon film to a thickness andthen smoothing the silicon film surface. Optionally, the silicon film isprotected with an encapsulation layer after being thinned and smoothed.A silicon film that can be treated using the exemplary embodiments ofthe present invention includes a silicon film in an SOI substrate orsilicon films on other type of well-known substrates.

[0027] Throughout the following discussion, the term “silicon film”generally refers to a silicon film, a silicon alloy film, or any othersilicon containing film (e.g., silicon germanium film). The silicon filmmay be of any crystalline form such as an amorphous, polycrystalline andmonocrystalline. The silicon film may be formed on or be part of anywell known substrate such as an oxide film, an SOI substrate, etc. Theterm “silicon film surface” generally refers to a surface of suchsilicon film described above. Additionally, the term “H₂:HCl etchingprocess” refers to an etching process that uses a gas mixture thatcomprises a hydrochloric acid and a hydrogen (H₂) gases.

[0028] In one embodiment, a silicon film is provided. The silicon filmis thinned using a gas cluster ion beam (GCIB) etching process. Thesilicon film is then smoothed using a smoothing process. Examples of asmoothing process that can be used include an H₂:HCl etching process andan annealing process.

[0029] In another embodiment, a silicon film is provided. The siliconfilm is thinned and at the same time, an intended non-uniformity profileis incorporated into the silicon film. The silicon film is then smoothedusing a smoothing process. An example of a process that can incorporatethe intended non-uniformity profile is a GCIB etching process. And,examples of a smoothing process that can be used include an H₂:HCletching process and an annealing process. The reason for incorporatingthe intended non-uniformity profile and then smooth out the intendednon-uniformity profile will be apparent from the discussion below.

[0030]FIG. 1A illustrates an exemplary method 11 of treating a siliconfilm. In the method 11, at operation 13, a silicon film is provided. Aninitial mean thickness of the silicon film is obtained at operation 15using conventional methods such as a reflectometry technique. An initialnon-uniformity profile for the silicon film is obtained at operation 17using conventional methods such as the reflectometry technique used forthe operation 15. The silicon film is then thinned to a thickness and atthe same time, an intended non-uniformity profile is incorporated intothe silicon film surface at operation 19. A process such as the GCIBetching process is used to thin the silicon film and incorporate theintended non-uniformity profile. At operation 21, the silicon filmsurface is smoothed using a smoothing process having a smoothing profilethat compensates for the intended non-uniformity profile. An example ofsuch a smoothing process is an H₂:HCl etching process. Thinning thesilicon film with the GCIB etching process alone gives good uniform filmthickness but not surface smoothness. Smoothing the silicon film alonedoes not give a uniform thickness across the film. Further, a smoothingprocess such as the H₂:HCl etching process inherently has an etchingprofile. The GCIB etching process can be used to incorporate an intendednon-uniformity profile that will be smoothed out by the H₂:HCl etchingprocess. The resulting film is thinned to a uniform and controlthickness and a good smoothness across the film. Optionally, anencapsulation film (e.g., a silicon dioxide film) is formed over thesilicon film that has been treated with the GCIB etching and thesmoothing processes as illustrated at operation 23.

[0031]FIG. 1B illustrates an exemplary method 100 of treating a siliconfilm. In the method 100, the silicon film is first thinned to athickness using a GCIB etching process and then smoothed using asmoothing process. A smoothing process that can be used includes anH₂:HCl etching process.

[0032] At operation 102 of the method 100, the initial non-uniformity ofthe surface of the silicon film is determined. A conventional measuringtechnique is used to map the initial non-uniformity of the silicon filmsurface to obtain the initial non-uniformity mapping information. Atoperation 104, a predetermined or an intended non-uniformity mappinginformation for an intended non-uniformity profile is created. Thisintended non-uniformity profile is incorporated into the silicon filmsurface during the thinning process of the silicon film.

[0033] At operation 106, a GCIB etching process (see below) is used tothin the silicon film to a thickness and to incorporate the intendednon-uniformity profile into the silicon film surface. In one embodiment,a GCIB is directed toward the silicon film surface. The GCIB ismodulated depending on the initial non-uniformity mapping informationand the intended non-uniformity mapping information such that thesilicon film is thinned and the intended non-uniformity profile isincorporated into the silicon film.

[0034] At operation 108, the thinned silicon film is smoothed out usinga smoothing process that has a smoothing profile that compensates forthe intended non-uniformity profile. The smoothing profile of thesmoothing process compensates for the intended non-uniformity in thatthe smoothing process smoothes out the intended non-uniformity profile.To smooth out the thinned silicon film, an H₂:HCl etching process isused wherein the silicon film surface is etched a high temperature andin the presence of a hydrogen (H₂) and hydrochloric acid (HCl) gasmixture. The method 100 takes advantage of the fact that the GCIBetching process can thin a film to a uniform thickness across the filmbut not necessarily leaves a very smooth surface. The method 100 furthertakes advantage of the fact that (1) the H₂:HCl etching process etches afilm with an etching profile that can be determined and (2) a filmtreated by the H₂:HCl etching process has a very smooth surface.Combining the GCIB etching process with the H₂:HCl etching process, themethod 100 thins the silicon film to a thickness and incorporates theintended non-uniformity profile that is smoothed out using the H₂:HCletching process. The silicon film treated with the GCIB and the H₂:HCletching processes is very smooth and has a uniform thickness. In oneembodiment, the silicon film is less than 200 Å thick and is very smooth(e.g., having a surface roughness less than 1 Å RMS).

[0035] At operation 110, an encapsulation film (e.g., a silicon dioxidefilm) is optionally formed over the silicon film that has been treatedwith the GCIB etching and the smoothing processes. In one embodiment, toform the encapsulation layer on the silicon film, an ozone (O3) gas isused. The silicon film is “soaked” with the ozone gas. The ozone gasforms a stable and clean oxide layer on the silicon film. The siliconfilm is thus protected from contaminants by an oxide film that has ahigh density, high purity, and high quality.

[0036] The exemplary methods of the present invention optimizeadvantages of both the GCIB etching process and the smoothing process.The GCIB etching process has an excellent thickness control. And, thesmoothing process has an excellent smoothness control. The silicon filmtreated with these two processes has a uniform thickness and a smoothsurface. Additionally, the silicon film is protected with a high qualityencapsulation film.

[0037] As a thinning technique, the GCIB etching process has anadvantage in that the GCIB etching process can selectively removematerial to thin a film to any thickness. A uniform film thickness isachieved by several steps. Based on the measured initial film thickness,more or less of the film material is removed at particular locations. Aprofile of the initial non-uniformity of the silicon film is programmedinto the GCIB etching process. A thickness and a desired profile arealso programmed into the GCIB etching process. This initialnon-uniformity profile is then considered for the etching or thethinning of the film to obtain the thickness and the desired profile.Thus, the GCIB etching process allows for more or less removal of thematerials according to the initial non-uniformity profile to thin thesilicon film to obtain the thickness and desired profile. In oneembodiment, the GCIB process' ability to control the thickness of thefilm allows for an incorporation of a particular intended non-uniformityprofile into the film.

[0038] As a smoothing process, the H₂:HCl etching process has excellentsmoothness control. For example, the H₂:HCl etching process is verystable and has a known etching profile that can be obtained for aparticular etching chamber. Thus, it is easy to create the intendednon-uniformity profile that the H₂:HCl etching process can compensatefor during the smoothing process.

[0039] Thus, the exemplary methods 11 and 100 take advantage of theprecise thickness control of the GCIB etching process and the surfacesmoothing ability of the H₂:HCl etching process.

[0040]FIG. 1C illustrates an exemplary method 10 of treating a siliconfilm. In the method 10, at operation 12, a silicon film is provided. AGCIB etching process is used to thin the silicon film as illustrated atoperation 14. At operation 16, the silicon film surface is smoothedusing an annealing process. Optionally, an encapsulation film (e.g., asilicon dioxide film) is formed over the silicon film that has beentreated with the GCIB etching and the smoothing processes as illustratedat operation 16.

[0041]FIG. 1D illustrates an exemplary method 10A of treating a siliconfilm. In the method 10A, at operation 20, a silicon film is provided. Aninitial mean thickness of the silicon film is obtained at operation 22using conventional methods such as a reflectometry technique. An initialnon-uniformity profile for the silicon film is obtained at operation 24using conventional methods such as the reflectometry technique used forthe operation 22. The silicon film is then thinned to a thickness usinga GCIB etching process as illustrated at operation 26. At operation 28,the silicon film surface is smoothed using an annealing process such asa rapid thermal annealing process. Optionally, an encapsulation film(e.g., a silicon dioxide film) is formed over the silicon film that hasbeen treated with the GCIB etching and the smoothing processes asillustrated at operation 30.

[0042] As a smoothing process, a rapid thermal annealing has excellentcapability of smoothing a rough surface. The annealing process cansmooth a film surface by re-arranging the surface atoms. The annealingprocess can this smooth out roughness that is present on the siliconfilm after being treated by a GCIB etching process.

[0043] Thus, the exemplary methods 10 and 10A take advantage of theprecise thickness control of the GCIB etching process and the surfacesmoothing ability of the annealing process.

[0044]FIG. 2A illustrates another exemplary method, a method 101, oftreating a silicon film by thinning while incorporating an intendednon-uniformity profile into the surface of the silicon film and thensmoothing out the intended non-uniformity profile. In one embodiment,the silicon film is formed on a semiconductor substrate typically usedfor making semiconductor devices. At operation 120, the initial meanthickness of the silicon film is measured. At operation 122, an initialnon-uniformity of the silicon film is mapped to create an initialnon-uniformity mapping information. In one embodiment, the initial meanthickness of the silicon film is first calculated. Thickness of varioussections across the silicon film are then measured and compared to theinitial mean thickness. An initial non-uniformity mapping information iscreated based on the different thickness across the silicon film. In oneembodiment, the initial non-uniformity mapping information indicates ainitial non-uniformity profile across the silicon film.

[0045] In one embodiment, a non-uniformity profile for the H₂:HCletching process can be determined at operation 126. The non-uniformityprofile for the H₂:HCl etching profile can be determined based on theetching profile of the H₂:HCl etching process for a particular processchamber. In one embodiment, the silicon film's thickness before andafter being etched by a particular H₂:HCl etching process is measuredwith a conventional reflectometry instrument. The thickness measurebefore and after the hydrogen hydrochloride enables the determination ofthe particular H₂:HCl etching process.

[0046] In one embodiment, at operation 128, an intended non-uniformitymapping information is created. In one embodiment, the intendednon-uniformity mapping information is created based on thenon-uniformity profile of the H₂:HCl etching process. This intendednon-uniformity mapping information indicates the etching profile of theH₂:HCl etching process. In another embodiment, the intendednon-uniformity mapping information simply represents a roughness on asurface that the annealing process is capable of smoothing out.

[0047] At operation 130, a scanning program for a GCIB etching processis created. This scanning program is used to thin the silicon film andincorporate an intended non-uniformity profile into the silicon filmsurface. The scanning program is created based on the initialnon-uniformity mapping information and the intended non-uniformitymapping information created at operation 128. In one embodiment, atoperation 132, the scanning program created at operation 130 is storedinto a controller that runs the GCIB etching process.

[0048] In one exemplary embodiment, the substrate with the silicon filmto be etched or thinned is loaded into the GCIB chamber at operation134. The controller is then executed as illustrated operation 136. Whenthe controller is executed, the scanning program is executed toselectively etch regions of the silicon film to achieve the thicknessand to incorporate the intended non-uniformity profile into the siliconfilm surface. The scanning program dictates how much material from aparticular region that is removed to thin the silicon film to thethickness and at the same time incorporate the intended non-uniformityprofile into the surface of the silicon film. At operation 138, thesubstrate is removed from the GCIB chamber once the silicon film hasbeen thinned. The silicon film that has been processed according to themethod 101 as discussed above is referred to as a GCIB treated siliconfilm.

[0049] The GCIB treated silicon film is then smoothed to produce athinned and smoothed silicon film. In one embodiment, a method 103described in FIG. 2B is used to smooth the GCIB treated silicon film. Atoperation 142 of the method 103, the substrate with the GCIB treatedsilicon film is placed in a smoothing chamber. The GCIB treated siliconfilm is smoothed out using an H₂:HCl etching process as illustrated atoperation 154. In one embodiment, the H₂:HCl etching process includes anaddition of a silicon source gas (e.g., silane, disilane, etc.).

[0050] In one embodiment, the substrate is heated to a temperaturebetween 1000° C. to 1300° C. for the H₂:HCl etching process asillustrated at operation 157. While the substrate is heated, the surfaceof the treated GCIB silicon film is exposed to a gas mixture comprisingof hydrogen (H₂) and hydrochloric gas (HCl) gas as illustrated atoperation 158. The relatively high temperature used during the surfacetreatment is sufficient to increase silicon mobility and thereby causingthe silicon in high areas of peaks to migrate to low areas or valleys inthe silicon film. Simultaneously, with the silicon migration, the gasmixture removes the top regions of the silicon surface resulting in asmoothing of the silicon surface. At operation 160, after the surface ofthe silicon film has been sufficiently smoothed to a roughness value ofless than 1 Å RMS when the H₂:HCl etching process is ended. In oneembodiment, the H₂:HCl etching process etches and smoothes the siliconfilm. The thickness of the silicon film is reduced at a rate of 0.1Å/second to more than 1000 Å/second depending on the proportion of theHCl in the gas mixture.

[0051] In one embodiment, a conventional chemical vapor depositionchamber can be used for the H₂:HCl etching process. In another example,a single wafer deposition chamber is used. In yet other examples, anyapparatus conventionally used for a H₂:HCl etching process can be usedto smooth the GCIB treated silicon film. An example of a single waferdeposition chamber that can be used includes the Applied Materialssingle wafer atmospheric “EPI” tool known as the “EPI Centura”. Anexample of a single wafer deposition chamber will be described below.

[0052] As mentioned, the H₂:HCl etching process has an etching profilethat compensates for the intended non-uniformity profile. Thus, theetching profile of the H₂:HCl etching process smoothes out the intendednon-uniformity profile to leave the GCIB treated silicon film with asmooth surface. In one embodiment, an Atomic Force Microscopy (AFM) isused to measure the smoothness (by measuring the surface roughness) ofthe silicon film after it is treated with the GCIB and the H₂:HCletching processes. In one embodiment, the final film has a surfaceroughness less than 1 Å RMS.

[0053] In another exemplary embodiment, the silicon film that is thinnedand smoothed according to the exemplary embodiments described above canact as a layer that other silicon films can be deposited or formedthereon. In one embodiment, an encapsulation film is formed on thesilicon film to protect the silicon film. In this embodiment, thesubstrate is placed in a chamber that is coupled to an ozone generatorthat can generate an ozone gas from an oxygen source gas (see below FIG.5B). The oxygen source gas may comprise a substantially pure oxygen gas.In one embodiment, the oxygen gas has a purity of 99.999%. The ozonegenerator supplies the ozone gas into the chamber to soak the siliconfilm with the ozone gas. The encapsulation film is a clean and stablesilicon dioxide formed on the silicon film. The encapsulation filmprotects the silicon film from contaminants so that the silicon film maybe exposed to air until being used to form devices therein and thereon.An example of a chamber that can be used to form the encapsulation filmcan be found in U.S. Pat. No. 6,376,387, which is assigned to AppliedMaterials.

[0054]FIG. 2C illustrates another exemplary method, a method 105, oftreating a silicon film. In one embodiment, the silicon film is formedon a semiconductor substrate typically used for making semiconductordevices. At operation 170, the initial mean thickness of the siliconfilm is measured. At operation 172, an initial non-uniformity of thesilicon film is mapped to create an initial non-uniformity mappinginformation. In one embodiment, the initial mean thickness of thesilicon film is first calculated. Thickness of various sections acrossthe silicon film are then measured and compared to the initial meanthickness. An initial non-uniformity mapping information is createdbased on the different thickness across the silicon film. In oneembodiment, the initial non-uniformity mapping information indicates aninitial non-uniformity thickness profile across the silicon film.

[0055] At operation 174, a scanning program for a GCIB etching processis created using techniques known in the art. This scanning program isused to thin the silicon film. The scanning program is created based onthe initial non-uniformity mapping information and a thickness that thesilicon film needs to be thinned to. In one embodiment, at operation176, the scanning program created at operation 174 is stored into acontroller that runs the GCIB etching process.

[0056] In one exemplary embodiment, the substrate with the silicon filmto be etched or thinned is loaded into the GCIB chamber at operation178. The controller is then executed as illustrated operation 180. Whenthe controller is executed, the scanning program is executed toselectively etch regions of the silicon film to achieve the thicknessthat the silicon film needs to be at. In one embodiment, the siliconfilm is thinned to a thickness less than 200 Å. The scanning programdictates how much material from a particular region that is removed tothin the silicon film to the thickness and at the same time incorporatethe intended non-uniformity profile into the surface of the siliconfilm. At operation 182, the substrate is removed from the GCIB chamberonce the silicon film has been thinned.

[0057] As can be seen the exemplary method 105 the GCIB etching processallows the etching of the silicon film to the thickness by etching moreor less at a certain location of the silicon film depending on theinitial non-uniformity mapping information and the intendednon-uniformity mapping information that have been stored into thescanning program. The GCIB etching process has the ability to finelycontrol the etching of the silicon film to a thin or even an ultra thinlevel. For example, the silicon film can be etched or thinned to athickness less than 200 Å. The silicon film that has been processedaccording to the method 105 as discussed above is referred to as a GCIBtreated silicon film.

[0058] The GCIB treated silicon film is then smoothed to produce athinned and smoothed silicon film. In one embodiment, the substrate withthe GCIB treated silicon film is placed in an annealing chamber asillustrated at operation 184.

[0059] The annealing process can be carried out using a conventionalrapid thermal annealing process chamber (annealing chamber). In oneembodiment, as shown at operation 186, the substrate is heated to atemperature between 1000° C. and 1300° C. The annealing process can becarried out at a sub-atmospheric pressure, for example, less than 760Torr. Additionally, as shown at operation 188, a gas mixture containinggases such as hydrogen (H₂), oxygen (O₂), nitrogen (N₂), helium (He), orargon (Ar) is introduced into the annealing chamber. In an embodimentwhere the annealing is carried out with a mixture containing H₂ gas,during the annealing process, the annealing process induces a surfacediffusion phenomenon of Silicon atoms leading to smoothing the siliconfilm surface. The substrate is annealed for a predetermined amount oftime of annealing, for example, 10 to 60 seconds. The annealing processis ended at operation 190. In one embodiment, the substrate is annealedfor a sufficient amount of time to obtain a roughness value of less than1 Å RMS.

[0060]FIG. 3 illustrates an exemplary GCIB apparatus 2000 which can beused to thin the silicon film in accordance with some of the exemplaryembodiments described above, for example, the method 100 and the method101. FIG. 4 illustrate an exemplary thermal processing apparatus 210 inwhich some of the embodiments can be implemented, for example, themethod 103 described above. An example of such an apparatus shown FIG. 4is the Applied Materials single wafer atmospheric “EPI” tool known asthe “EPI Centura”. It is to be appreciated that other processingchambers can also be used for the exemplary embodiments of the presentinvention such as a resistively heated single wafer deposition chamberor a rapid thermal annealing (RTA) chamber. These chambers are wellknown in the art thus, descriptions of these chambers are not included.

[0061] Returning to FIG. 3, in one exemplary embodiment, a conventionalGCIB apparatus 2000 includes a vacuum vessel 2102, which is divided intothree communicating chambers, a source chamber 2104, anionization/acceleration chamber 2106, and a processing chamber 2108. TheGCIB apparatus 2000 includes three vacuum pumping systems, 2146A, 2146B,and 2146C, which are used to evacuate the pressure in the vessel 2102.The GCIB apparatus 2000 is further coupled to a gas source, cylinder2111 to supply gas into the vessel 2102. The vessel 2102 includes anionizer 2122 to ionize the gas clusters and a filament power supply 2136to accelerate the gas clusters. The vessel 2102 further includes asubstrate holder 2150, which can hold a substrate 2152. Further detailsof a conventional GCIB apparatus can be found in a PCT ApplicationPCT/US01/21620 (WO 02/05315), published Jan. 17, 2002 and U.S. Pat. No.6,207,282.

[0062] In another exemplary embodiment, the source chamber 2104, theionization/acceleration chamber 2106, and the processing chamber 2108are evacuated to suitable operating pressures by the vacuum pumpingsystems 2146A, 2146B, and 2146C, respectively. The chambers aretypically operated under a sub-atmospheric pressure. To begin theprocess, a condensable source gas 2112 stored in the cylinder 2111 isadmitted under pressure through gas metering valves 2113 and gas feedtube 2114 into the source chamber 2104 of the vessel 2102. Suitablecondensable source gases 2112 include, but are not necessarily limitedto argon (AR), nitrogen (N₂), carbon dioxide (CO₂), and oxygen (O₂). Thecondensable source gas 2122 enters a stagnation chamber 2116 and isinjected into the substantially lower pressure vacuum through a properlyshaped nozzle 2110. The injected condensable source gas 2112 forms asupersonic gas jet 2118. Expansion in the gas jet 2118 results incooling of the gas jet 2118 and causes a portion of the gas jet 2118 tocondense into clusters, each of which consisting of from several toseveral thousand weakly bound atoms or molecules. The source chamber2104 also includes a gas skimmer aperture 2120, which partiallyseparates the gas molecules that have not condensed into a cluster jetfrom the cluster jet so as to minimize pressure in the downstreamregions. High pressures would be detrimental to the ionizer 2122, thehigh voltage electrodes 2126, and the process chamber 2108.

[0063] After the supersonic gas jet 2118 containing gas clusters havebeen formed, the clusters are ionized in an ionizer 2122 in theionization/acceleration chamber 2106. The ionizer 2122 is typically anelectron impact ionizer that produces thermoelectrons from one or moreincandescent filaments 2124. The ionizer 2122 also accelerates anddirects the electrons causing them to collide with the gas clusters inthe gas jet 2118, when a gas jet 2188 passes through the ionizer 2122.The electron impact ejects the electrons from the clusters, causing aportion of the clusters to become positively ionized. A set of suitablybiased high voltage electrodes 2126 extracts the cluster ions from theionizer to form a beam. The high voltage electrode 2126 then acceleratesthe cluster ions in a beam in to a desired energy (typically from 1 keVto several tens of keV) and focuses the cluster ions them to form a GCIB2128 having an initial trajectory 2154.

[0064] A filament power supply 2136 included in the ionizer provides avoltage V₂ to heat the ionizer incandescent filament 2124. An anodepower supply 2134 provides a voltage V₁ to accelerate thermoelectronsemitted from the filament 2124 to cause the thermoelectrons to bombardthe cluster containing gas jet 2118 to produce the ions.

[0065] An extraction power supply 2138 coupling to the high voltageelectrodes 2126 provides a voltage V₃ to bias a high voltage electrodeto extract ions from the ionizing region of ionizer 2122 and to form theGCIB 2128. An accelerator power supply 2140 provides a voltage V₄ tobias a high voltage electrode with respect to the ionizer 2122 so as toresult in a total GCIG acceleration energy equal to the V₄ electronvolts (eV) and, lens power supplies 2142 and 2144 may be provided tobias high voltage electrodes with potentials V₆ and V₅, respectively, tofocus the GCIB 2128.

[0066] In one exemplary embodiment, a substrate 2152, is held on asubstrate holder 2150, as illustrated in FIG. 3. The substrate 2152 canbe a treated using the GCIB etching process. In one embodiment, thesubstrate 2152 is exposed within the path of the GCIB 2128. In oneexemplary embodiment, a scanning system is used to uniformly scan theGCIB 2128 across large areas of the substrate 2152. In this embodiment,two pairs of orthogonally oriented electrostatic scan plates 2130 and2132 are included in the processing chamber 2108. The electrostatic scanplates 2130 and 2132 can be utilized to produce a raster or otherscanning pattern across the desired processing area on the substrate2152. When beam scanning is performed, a scan generator 2156 providesX-axis and Y-axis scanning signal voltage to the pairs of electrostaticscan plates 2130 and 2132 through lead pairs 2158 and 2160 respectively.The scanning signal voltages are commonly triangular waves of differentfrequencies that cause the GCIB 2128 to be converted into a scanned GCIB2148, which scans the entire surface of the substrate 2152.

[0067] In another exemplary embodiment, the GCIB apparatus 2000 shown inFIG. 3 includes a system controller 2050, which controls variousoperations of the apparatus 2000. In one exemplary embodiment, thesystem controller 2050 includes a machine-readable medium 2052 such as ahard disk drive (indicated in FIG. 4 as “memory 2052”) or a floppy diskdrive. The system controller 2050 also includes a processor 2054. Aninput/output device 2056 such as a CRT monitor and a keyboard is used tointerface between a user the and the system controller 2050.

[0068] The processor 2054 contains a single board computer (SBC), analogand digital input/output boards, interface boards and stepper motorcontroller board. Various parts of the GCIB apparatus 2000 conform tothe Versa Modular Europeans (VME) standard which defines board, cardcage, and connector dimensions and types. The VME standard also definesthe bus stricture having a 16-bit data bus and 24-bit address bus.

[0069] In one exemplary embodiment, the system controller 2050 controlsall of the activities of the GCIB apparatus 2000. The system controllerexecutes system control software, which is a computer program stored inthe machine-readable medium 2052. Preferably, the machine-readablemedium 2052 is a hard disk drive, but the machine-readable medium 2052may also be other kinds of memory stored in other kinds ofmachine-readable media such as one stored on another memory deviceincluding, for example, a floppy disk or another appropriate drive. Thecomputer program includes sets of instructions that dictate theparameters of a particular GCIB etching process.

[0070] The process for etching or thinning a silicon surface inaccordance with the present invention can be implemented using acomputer program product (program), which is stored in themachine-readable medium 2052 and, is executed by the processor 2054. Thecomputer program code can be written in any conventional computerreadable programming language, such as, 68000 assembly language, C, C++,Pascal, Fortran, or others. Suitable program code is entered into asingle file, or multiple files, using a conventional text editor, andstored or embodied in a computer usable medium, such as a memory systemof the computer. If the entered code text is in a high level language,the code is compiled, and the resultant compiler code is then linkedwith an object code of precompiled windows library routines. To executethe linked compiled object code, the system user invokes the objectcode, causing the computer system to load the code in memory, from whichthe CPU reads and executes the code to perform the tasks identified inthe program. Also stored in the machine-readable medium 2052 are processparameters to carry out the etching or thinning of the silicon films inaccordance with the exemplary embodiments of the present invention.

[0071] In one embodiment, the program includes instructions forreceiving an initial non-uniformity mapping information for the siliconfilm and an intended non-uniformity mapping information to beincorporated into the silicon film. The program may include instructionsfor receiving a scanning program which is created based on the initialnon-uniformity mapping information and the intended non-uniformitymapping information. In an embodiment, the program includes instructionsfor creating the scanning program based on the initial non-uniformitymapping information and the intended non-uniformity mapping information.The program may include instructions for treating a silicon film such asto thin the silicon film to a thickness and to incorporate an intendednon-uniformity profile into the silicon film as mentioned above.

[0072]FIG. 4 illustrates an exemplary apparatus for smoothing theintended non-uniformity profile that is incorporated into the siliconfilm using the GCIB etching process described above. In one embodiment,an H₂:HCl etching process is carried out in the apparatus shown in thisfigure. FIG. 4 illustrates an apparatus 210, which is a depositionreactor that can be used to smooth out the silicon film surface that hasthe intended non-uniformity profile. The apparatus 210 comprises adeposition chamber 212 having an upper dome 214, a lower dome 216, and asidewall 218 between the upper and lower domes 214 and 216. Coolingfluid (not shown) is circulated through sidewall 218 in order to coolthe sidewall 218. An upper liner 282 and a lower liner 284 are mountedagainst the inside surface of the sidewall 218. The upper and lowerdomes 214 and 216 are made of a transparent material to allow heatinglight to pass through into the chamber 212.

[0073] Within the chamber 212 is a fiat, circular susceptor 220 forsupporting a wafer (or a semiconductor substrate) in a horizontalposition. The susceptor 220 extends transversely across the chamber 212at the sidewall 218 to divide the chamber 212 into an upper portion 222above the susceptor 220 and a lower portion 224 below the susceptor 220.The susceptor 220 is mounted on a shaft 226 which extendsperpendicularly downwardly from the center of the bottom of thesusceptor 220. The shaft 226 is connected to a motor (not shown) whichrotates the shaft 226 in order to rotate the susceptor 220. The wafersupported by the susceptor 220 is rotated throughout the smoothingprocess. An annular preheat ring 228 is connected at its outer peripheryto the inside periphery of the lower liner 284 and extends around thesusceptor 220. The pre-heat ring 228 is in the same plane as thesusceptor 228 with the inner edge of the pre-heat ring 228.

[0074] An inlet manifold 230 is positioned in the side of the chamber212 and is adapted to admit gas from a source of gas or gases, such astanks 140, into the chamber 212. An outlet port 232 is positioned in theside of chamber 212 diagonally opposite the inlet manifold 230 and isadapted to exhaust gases from the deposition chamber 212.

[0075] A plurality of high intensity lamps 234 are mounted around thechamber 212 and direct their light through the upper and lower domes 214and 216 onto the susceptor 220 (and the preheat ring 228) to heat thesusceptor 220 (and the preheat ring 228). The susceptor 220 and thepreheat ring 228 are made of a material, such as silicon carbide, coatedgraphite which is opaque to the radiation emitted from the lamps 234 sothat they can be heated by radiation from the lamps 234. The upper andlower domes 214 and 216 are made of a material which is transparent tothe light of the lamps 234, such as clear quartz. The upper and lowerdomes 214 and 216 are generally made of quartz because quartz istransparent to light of both visible and IR frequencies. Quartz exhibitsa relatively high structural strength; and it is chemically stable inthe process environment of the deposition chamber 212. Although lampsare the preferred elements for heating wafers in deposition chamber 212,other methods may be used such as resistance heaters and Radio Frequencyinductive heaters.

[0076] An infrared temperature sensor 236 such as a pyrometer is mountedbelow the lower dome 216 and faces the bottom surface of the susceptor220 through the lower dome 216. The temperature sensor 236 is used tomonitor the temperature of the susceptor 220 by receiving infraredradiation emitted from the susceptor 220 when the susceptor 220 isheated. A temperature sensor 237 for measuring the temperature of awafer may also be included if desired.

[0077] An upper clamping ring 248 extends around the periphery of theouter surface of the upper domes 214. A lower clamping ring 250 extendsaround the periphery of the outer surface of the lower dome 216. Theupper and lower clamping rings are secured together so as to clamp theupper and lower domes 214 and 216 to the sidewall 218.

[0078] The gas inlet manifold 230 included in the apparatus 210 feedsprocess gas (or gases) into the chamber 212. The gas inlet manifold 230includes a connector cap 238, a baffle 274, and an insert plate 279positioned within the sidewall 218. Additionally, the connector cap 238,the baffle 274, and the insert plate 279 are positioned within a passage260 formed between upper liner 282 and lower liner 284. The passage 260is connected to the upper portion 222 of chamber 212. Process gas (orgases) are introduced into the chamber 212 from the gas cap 238, the gasor gases are then flown through the baffle 274, through the insert plate279, and through the passage 260 and then into the upper portion 222 ofchamber 212.

[0079] The apparatus 210 also includes an independent gas inlet 262 forfeeding a purge gas, such as hydrogen (H₂) or Nitrogen (N₂), into thelower portion 224 of deposition chamber 212. As shown in FIG. 4, thepurge gas inlet 262 can be integrated into gas inlet manifold 230, ifdesired, as long as a physically separate and distinct passage 262through the baffle 274, the insert plate 279, and the lower liner 284 isprovided for the purge gas, so that the purge gas can be controlled anddirected independent of the process gas. The purge gas inlet 262 neednot be integrated or positioned along with deposition gas inlet manifold230, and can, for example, be positioned on the reactor 210 at an angleof 90° from a deposition gas inlet manifold 230.

[0080] As mentioned, the apparatus 210 also includes a gas outlet 232.The gas outlet 232 includes an exhaust passage 290, which extends fromthe upper chamber portion 222 to the outside diameter of sidewall 218.The exhaust passage 290 includes an upper passage 292 formed between theupper liner 282 and the lower liner 284 and which extends between theupper chamber portion 222 and the inner diameter of sidewall 218.Additionally, the exhaust passage 290 includes an exhaust channel 294formed within the insert plate 279 positioned within sidewall 218. Avacuum source, such as a pump (not shown) for creating low or reducedpressure in the chamber 212 is coupled to the exhaust channel 294 on theexterior of sidewall 218 by an outlet pipe 233. The process gas (orgases) fed into the upper chamber portion 222 is exhausted through theupper passage 292, through the exhaust channel 294 and into the outletpipe 233.

[0081] The gas outlet 232 also includes a vent 296, which extends fromthe lower chamber portion 224 through lower liner 284 to the exhaustpassage 290. The vent 296 preferably intersects the upper passage 292through the exhaust passage 290 as shown in FIG. 4. The purge gas isexhausted from the lower chamber portion 224 through the vent 296,through a portion of the upper chamber passage 292, through the exhaustchannel 294, and into the outlet pipe 233. The vent 296 allows for thedirect exhausting of the purge gas from the lower chamber portion to theexhaust passage 290.

[0082] According to some exemplary embodiment of the present invention,the process gas or gases 298 are fed into the upper chamber portion 222from gas inlet manifold 230. In some exemplary embodiments, the processgas is defined as the gas or gas mixture which acts to remove, treat, ordeposit a film on a wafer or a substrate that is placed in chamber 212.In one embodiment, the process gas comprises a hydrochloric (HCl) gasand an gas, such as H₂. In this example the hydrochloric gas and the H₂gas are used as an etchant mixture to smooth the silicon surface of thesilicon film that has been thinned using the GCIB etching process thathas been described above.

[0083] In one exemplary embodiment, while the process gas is fed intothe upper chamber portion 222, an inert purge gas or gases 299 are fedindependently into the lower chamber portion 224. Purging the chamber212 with the purge gas 299 prevents an unwanted reaction at the bottomside of the chamber 212 or the bottom side of the susceptor 220.

[0084] In one exemplary embodiment, the apparatus 210 shown in FIG. 4 isa single wafer reactor that is also “cold wall” reactor. The sidewall218 and upper and lower liners 282 and 284, respectively, are at asubstantially lower temperature than the preheat ring 928 and thesusceptor 220 (and a wafer placed thereon) during processing. Forexample, when a H₂:HCl etching process occurs at a process temperaturebetween 1100° C. and 300° C. the susceptor and the wafer are heated to atemperature between 1100° C. and 1300° C. while the sidewall and theliners are at a temperature of about 400-600° C. The sidewall 218 andliners 282 and 284 are at a cooler temperature because they do notreceive direct irradiation from lamps 234 due to reflectors 235, andbecause cooling fluid is circulated through the sidewall 218.

[0085] In another exemplary embodiment, the processing apparatus 210shown in FIG. 4 includes a system controller 150, which is similar tothe system controller 2050 that controls the GCIB apparatus 2000. Thesystem controller 150 controls various operations of the apparatus 210such as controlling gas flows into the chamber 212, controlling thesubstrate's temperature, controlling the susceptor 220's temperature,and controlling the chamber's pressure. In one exemplary embodiment, thesystem controller 150 includes a machine-readable medium 152 such as ahard disk drive (indicated in FIG. 4 as “memory 152”) or a floppy diskdrive. The system controller 150 also includes a processor 154. Aninput/output device 156 such as a keyboard, a mouse, a light pen, and aCRT monitor, is used to interface between a user the and the systemcontroller 150.

[0086] In one exemplary embodiment, the system controller 150 controlsall of the activities of the apparatus 210. The system controllerexecutes system control software, which is a computer program stored inthe machine-readable medium 152. Preferably, the machine-readable medium152 is a hard disk drive, but the machine-readable medium 152 may alsobe other kinds of memory stored in other kinds of machine-readable mediasuch as one stored on another memory device including, for example, afloppy disk or another appropriate drive. The computer program includessets of instructions that dictate the timing, mixture of gases, chamberpressure, chamber temperature, lamp power levels, susceptor position,and other parameters of a particular smoothing process.

[0087] The process for smoothing a silicon surface in accordance withthe present invention can be implemented using a computer programproduct, which is stored in the machine-readable medium 152 and, isexecuted by the processor 154. The computer program code can be writtenin any conventional computer readable programming language, such as,68000 assembly language, C, C++, Pascal, Fortran, or others. Also storedin the machine-readable medium 152 are process parameters such as theprocess gas flow rates (e.g., H₂ and HCl flow rates), the processtemperatures and the process pressure necessary to carry out thesmoothing of the silicon films in accordance with the exemplaryembodiments of the present invention.

[0088] FIGS. 6A-6K illustrate exemplary embodiments in which thecombination of the GCIB etching process and the annealing process or theH₂:HCl etching process is used to treat (e.g., thin and then smooth) thesilicon film of an SOI substrate or wafer. FIG. 5A accompanies FIGS.6A-6K in that FIG. 5A illustrates an exemplary cluster tool 500 that canbe utilized to carry the exemplary embodiments of FIGS. 6A-6K. Thefabrication of the SOI substrate will be described herein below after abrief discussion of the cluster tool 500. Although the exemplaryembodiments of the present invention focus on the treatment, e.g.,thinning and smoothing, of the silicon film on an insulator substrate,these exemplary embodiments can be used for treating other silicon filmswithout deviating from the scope of the present invention.

[0089] The cluster tool 500 includes a transfer chamber 502 to which areattached a plurality of different process apparatuses including, animplant chamber 504, a bond/cleave chamber 506, a GCLB chamber 507, asmoothing chamber 508, an oxide formation chamber 510, an annealingchamber 509, and a loadlock system 512. The GCIB chamber 507 can be theGCIB apparatus 2000 shown in FIG. 3. The smoothing chamber 508 can bethe single wafer chamber illustrated as the apparatus 210 shown in FIG.4. Other chambers, such as a cool down chamber or chambers and/oradditional loadlocks, can be attached to transfer chamber 502 asrequired.

[0090] In general, the implant chamber 504 is used to implant ions intoa donor wafer to form dislocations in a donor wafer to enable thesubsequent cleaving of the silicon film. The bond/cleave chamber 506 isused to bond the handle wafer to the implanted donor wafer and is usedto cleave the donor wafer from the handle wafer at the implantdislocation.

[0091] The GCIB chamber 507 is used to treat the silicon film that has arough cleaved surface following the bond and cleave process. The GCIBetching process occurring in the GCIB chamber 507 thins the siliconfilm, partially smoothes silicon surface (if necessary), andincorporates an intended uniformity profile into the silicon filmsurface. The silicon film can be thinned to a thickness (e.g., less than200 Å thick) and the surface of the silicon film has the intendednon-uniformity profile incorporated thereon.

[0092] The smoothing chamber 508 is used to smooth the surface of thesilicon film by smoothing out the intended non-uniformity profile thatis incorporated into the silicon film surface. In one embodiment, thesmoothing chamber 508 is a process chamber that can be used to carry outa H₂:HCl etching process which can smooth and thin the silicon film. Thesmoothing chamber 508 can also be used to deposit an epitaxial siliconfilm on the thinned and smoothed silicon surface if necessary since thesmoothing chamber 508 is also a conventional deposition chamber. Thesmoothing chamber 508 can also be used to smooth the silicon surface ofthe donor wafer and to deposit additional silicon thereon if desired.

[0093] The oxide formation chamber 510 is used to form an oxide on thedonor wafer (or handle water if desired). The oxide formation chamber510 can be for example, a thermal oxidation apparatus such as a furnaceor a rapid thermal processor in which a thermal oxide can be grown on asilicon film. Alternatively, the oxide formation chamber 510 can be achemical vapor deposition (CVD) apparatus.

[0094] The loadlock apparatus 512 is used to store wafers or substratesbefore they are processed in a particular chamber. A transfer chamber502 is also included in the cluster tool 500. The transfer chamber 502may include a wafer handling apparatus 501, which includes awafer-handling clip 503. The wafer handling apparatus 501 and thewafer-handling clip 503 facilitate the transport of wafer substrates inan out of the loadlock apparatus 512 and in and out of a particularprocess apparatus or chamber. The transfer chamber 502 is furtherattached to an exhaust system (not shown) such as a pump and a source ofinert gas, such as nitrogen (N₂) so that wafers can be transferredbetween the various process apparatuses or chambers in cluster tool 500in a reduced pressure ambient or in an inert ambient so that wafers arenot exposed to an oxidizing ambient or to sources of contamination.

[0095] The loadlock apparatus 512 can further be used as a chamber toform the encapsulation film. In one embodiment, the loadlock apparatus512 is used to form an encapsulation film on the silicon film after thesilicon film is treated with the GCIB etching process and the annealingprocess or the H₂:HCl etching process to protect the silicon film. Inthis embodiment, the substrate with the silicon film to be protected isplaced in the loadlock apparatus 512. An ozone gas is introduced intothe loadlock apparatus 512. The substrate is “soaked” with the ozonegas. The ozone gas forms a stable oxide layer that acts as anencapsulation layer to protect the silicon film. FIG. 5B illustrates anexemplary loadlock apparatus 512 in more detail. Details of an exampleof an apparatus that can be used to soak the substrate with the ozonegas to form the encapsulation film can be found in U.S. Pat. No.6,376,387, which is assigned to Applied Materials.

[0096] The loadlock apparatus 512 includes a loadlock chamber 552. Theloadlock chamber 552 stores from one to a plurality of substrates 580(e.g., wafers) to be processed by the cluster tool 500.

[0097] The loadlock apparatus 512 further includes an ozone generator560, which is coupled to an oxygen source gas 562. The oxygen source gas562 may comprise a substantially pure oxygen gas. In one embodiment, theoxygen gas has a purity of 99.999%. The ozone generator 560 generates anozone gas from the oxygen source gas 562. The ozone gas is metered intothe loadlock chamber 552 through an ozone supply valve 564 and an ozonesupply line 565.

[0098] The loadlock apparatus 512 further includes a nitrogen source gas566 which supplies nitrogen gas into the loadlock chamber 552 through anitrogen supply valve 568 and a nitrogen supply line 569.

[0099] The loadlock apparatus 512 also includes a pump 558 which can beused to control the pressure within the loadlock chamber 552. A pressuredetector 570 may also be included to monitor the pressure within theloadlock chamber 552.

[0100] There are advantages for forming the encapsulation oxide film inthe loadlock apparatus 512. One advantage is that another chamber thatis designated for a step in an existing process does not have to bededicated for exposing the substrate to the ozone gas. Another advantageis that such a system is relatively safe because there is asubstantially reduced likelihood that the ozone gas will mix withhydrogen gas within the cluster tool 500 and cause an explosion becausethe pressure within the loadlock apparatus 512 is always isolated fromthe area around the loadlock apparatus 512 when the ozone gas is withinthe loadlock apparatus 512 so that there is reduced likelihood that theozone gas will escape to a surrounding area and cause an explosion.Another advantage is that the overall time taken to process wafers orsubstrates is maintained.

[0101] In one exemplary embodiment, the loadlock apparatus 512 iscoupled to a controller 540. The controller 540 is similar to thecontrollers 2050 and 150 shown in FIGS. 3 and 4. The controller 540 istypically a computer having a processor (not shown) that can execute aprogram (a set of instructions) that controls all of the components ofthe cluster tool 500. The processor is similar to the processor 2054 and154 shown in FIGS. 3 and 4.

[0102] In one embodiment, the controller 540 controls the operations ofthe chambers that are included in the cluster tool 500 (e.g., chambers510, 509, 504, 506, 502, and 512). For example, the program receives aninput from the pressure detector 570 and controls all of the componentsbased on the pressure detected by the pressure detector 570.Additionally, the controller 540 controls the thinning of the substratein the GCIB chamber 507, the smoothing of the silicon film surface inusing the annealing process in the annealing chamber 509, and smoothingof the silicon film surface using the H₂:HCl etching process in thesmoothing chamber 508. Additionally, the controller 540 controls theforming of the encapsulation film on the silicon film in the loadlockapparatus 512. The process controller for the cluster tool 500 may alsocontrol the making of the SOI substrate according to the exemplaryembodiments described above.

[0103] FIGS. 6A-6K illustrate exemplary embodiments where an implant andcleave process is used to form an SOI substrate or wafer. In order toform wafer 650 as shown in FIG. 6A are provided. The donor wafer 650 isthe wafer (or substrate) that provides a layer or layers to betransferred. The handle wafer 600 is the wafer or substrate thatreceives the transferred layers from the donor wafer 650 and is thewafer which eventually becomes the substrate for the SOI substrate.

[0104] The handle wafer 600 includes a monocrystalline silicon substrate602. The silicon substrate 602 can be doped to any conductivity type(n-type or p-type) and to any conductivity level desired. In oneexemplary embodiment, the silicon substrate 602 is a p-type substratehaving a doping density of between 10¹⁵-10¹⁹ atoms/cm³. The handle wafer600 can also include an oxide film 604 formed thereon. In one exemplaryembodiment the oxide film 604 is between 1000-5000 Å thick. The oxidefilm 604 can be thermally grown by exposing silicon substrate 602 to anoxidizing ambient, such as oxygen (02), at a temperature between800-1250° C. in the oxide chamber 510.

[0105] The donor wafer 650 includes a monocrystalline silicon substrate652 with an oxide film 654 formed thereon. The silicon substrate 650 canbe doped to any desired conductivity type and level desired. In anembodiment of the present invention silicon substrate can be doped to alevel between 10¹⁵-10¹⁹ atoms/cm³. The oxide film 654 can be formed bythermally oxidizing a layer of the silicon substrate 650 in an oxidizingambient in the oxide chamber 510 as described above. The oxide film 654typically has a thickness between 1000-5000 Å.

[0106] In another exemplary embodiment, only one of the donor wafer 650or the handle wafer 600 has the oxide film grown thereon. Thus, only theoxide film 604 is crown on the handle wafer 600 or only the oxide film654 is grown on the donor wafer 650.

[0107] Next, as shown is FIG. 6B, the donor wafer 650 is implanted withions to form dislocation 656. To implant the ions, the donor wafer 650is moved into the implant chamber 504. The donor wafer 650 can beimplanted with hydrogen atoms or with inert ions such Argon (Ar) orHelium (He). In one exemplary embodiment, the donor wafer 650 is ionimplanted with a plasma immersion ion implantation process. Such aprocess can implant high doses of H₂ gas into the monocrystallinesilicon substrate 652 of the donor wafer 650. In such a process, a highvoltage negative bias is applied to the donor wafer 650 to acceleratethe ions towards the wafer face (the oxide film 654). The plasmaimmersion ion implantation process implants the entire donor wafersurface. In another exemplary embodiment, the P-III Ion ImplantationSystem developed by Silicon Genesis can be used for a plasma immersionion implantation step. Further yet, the ion implantation can be carriedout using, for example, beam line ion implantation equipmentmanufactured from companies such as Applied Materials, Axcelis Corp.,Varian, and others.

[0108] In one exemplary embodiment, the implantation of the hydrogenatoms generates an internal hydrogen rich layer 656 within the donorwafer 650. The depth, D, of the ion implantation peak determines theamount of silicon 658 which is subsequently removed from the siliconsubstrate 652 of the donor wafer 650. In one exemplary embodiment, thehydrogen ions are implanted between 1000-5000 Å into substrate 652 ofdonor wafer 650.

[0109] Next, the ion implanted donor wafer 650 and the handle wafer 600are bonded together. The ion implanted donor wafer 650 and the handlewafer 600 are placed into the bond/cleave chamber 506. In thebond/cleave chamber 506, the donor wafer 650 is bonded to the handlewafer 600 as shown in FIG. 6D. In one exemplary embodiment, the oxidefilm 654 of the donor wafer 650 is bonded to the oxide film 604 of thehandle wafer 600.

[0110] In one exemplary embodiment, the handle wafer 600 and the donorwafer 650 are bonded using a low temperature plasma activated bondprocess. By using plasma activation of the bond interface, higher bondstrength can be achieved at low process temperatures (e.g. roomtemperature). In this embodiment, and as shown in FIG. 6C, both thehandle wafer 600 and the donor wafer 650 are exposed to a lowtemperature plasma in order to generate plasma activated bondingsurfaces 606 and 660 respectably. It is to be appreciated that othersuitable bonding techniques may be used to bond the handle wafer to thedonor wafer.

[0111] In the bonding process, in one exemplary embodiment, the donorwafer 650 is flipped upside down so that bond interface 660 can beattached to the bond interface 606 of handle wafer 600 as shown in FIG.6D. The donor and handle wafer stack is then compressed together tosecurely bond the interface 660 and the interface 606 (indicated in FIG.6C). The plasma activation of the bond interface helps achieve asufficiently strong bonding for a subsequent room temperature cleavingprocess.

[0112] Next, as shown in FIG. 6E, the lower portion 659 of siliconsubstrate 652 of the donor wafer 650 is separated or cleaved from theupper portion of the silicon layer 658 at the dislocation 656 of thedonor wafer 650. In one exemplary embodiment, a Room TemperatureControlled Cleaved Process (RT/CCP) is used to separate the bonded pairat the implant dislocation 656 without using heat. The RT/CCP processinitiates a separation at one point on the wafer and propagates thatseparation cross the entire wafer through a mechanical cleaving method.In another exemplary embodiment and as shown in FIG. 6E, a nitrogen (N₂)stream is focused at the edge of the dislocation to cause theseparation.

[0113] The implant, bond, and cleave process transfers the oxide film654 and the silicon film 658 to the handle wafer 600. The transfergenerates an SOI substrate, which comprises a silicon wafer 602 with anoxide layer 669 (the combination of the oxide films 654 and 604) buriedunder a thin layer 658 of monocrystalline silicon. The thickness of thetop silicon layer 658 is determined by the depth of the hydrogenimplant. In one exemplary embodiment, the top silicon film 658 requiresfurther thinning to achieve a thickness, for example, a thickness lessthan 200 Å. The silicon film 658 also requires smoothing since thebonding and cleaving process leave the silicon film 658 with a roughsurface as shown in FIG. 6E.

[0114] As mentioned and as shown in FIG. 6E, the implant and cleaveprocess forms a very rough silicon surface 660, where silicon film 658is separated from silicon substrate 652. More thinning is typicallynecessary to produce a thin or ultra-thin silicon film 658. In oneembodiment, the desired final thickness of the silicon film 658 is lessthan 200 Å. The implant and cleave process typically forms a siliconsurface having a surface roughness of between 20-80 Å RMS. In order toprovide a suitable finish, the handle wafer 600 along with the oxidelayer 669 and the silicon 658 is first transferred into the GCIB chamberfor thinning.

[0115]FIG. 6F illustrates the SOI substrate with the rough silicon film658 that needs to be thinned and smoothed. Before thinning the siliconfilm 658 the initial thickness the silicon film 658 is measured. Theinitial non-uniformity of the silicon film 658 is also characterized.The characterization of the initial thickness and non-uniformity can bedone ex-situ to the GCIB chamber 507 or in-situ.

[0116] In one embodiment, the characterization of the initial thicknessand non-uniformity is done ex-situ using reflectometry or other suitableconventional techniques. The initial thickness and the non-uniformityacross the silicon film 658 allows for a determination of an initialnon-uniformity profile of the silicon film 658. In one exemplaryembodiment, a thickness measuring device such as the reflectometer isincluded in the cluster tool 500 as one of the process chamber. In oneembodiment, the reflectometry technique is used to measure thicknessacross the silicon film 658. The initial mean thickness of the siliconfilm 658 is then calculated based on the thickness measurements acrossthe silicon film 658. The reflectometry technique can produce apoint-by-point film thickness map of the silicon film 658 that may bereduced to a thickness contour graph. An example of such a contour graphis illustrated in FIG. 7.

[0117] In FIG. 7, the plus signs on the contour graph indicate that thesites with the plus signs are above (or thicker than) the calculatedmean thickness of the silicon film 658. The minus signs on the contourgraph indicate that the sites with the minus signs are below (or thinnerthan) the calculated mean thickness of the silicon film 658. In oneembodiment, the number of the sites of the silicon film 658 that aremeasured depends on the variation in thickness across the silicon film.For example, more sites can be measured if (1) the measurement is fast,and (2) the initial uniformity profile of the silicon film 658 has manyfeatures. The contour graph thus gives the initial non-uniformitymapping information of the silicon film 658. In another example, thecharacterization of the initial thickness and non-uniformity is donein-situ using a reflectometer or other suitable conventional techniquesthat are incorporated within the GCIB chamber 507.

[0118] The non-uniformity mapping information is stored as a series ofthickness points with precise wafer positions into a memory by acontroller. In one embodiment, an intended non-uniformity mappinginformation is created for an intended non-uniformity profile that is tobe incorporated into the silicon film 658. In one embodiment, theintended non-uniformity mapping information is created by experimentaldeterminations of an etching profile of an H₂:HCl etching process, whichis subsequently used to smooth the silicon film 658. For example, asillustrated in FIG. 6G, an intended non-uniformity profile 671 iscreated for the silicon film 658. In one embodiment, the intendednon-uniformity mapping information is stored as a series of thicknesspoints with precise wafer positions into the memory by the controller.

[0119] In one embodiment, a mathematical algorithm is then employedwhich takes the initial non-uniformity mapping information and theintended non-uniformity mapping information to create a scanning programthat has an etching pattern that is depended upon the initialnon-uniformity profile and the intended non-uniformity profile. Thescanning program thins the silicon film 658 and incorporates theintended non-uniformity profile into the surface of the silicon film 658as illustrated in FIG. 6H.

[0120] In another embodiment, a mathematical algorithm is employed whichtakes the initial non-uniformity mapping information to create ascanning program that has an etching pattern that is depended upon theinitial non-uniformity profile. The scanning program simply thins thesilicon film 658 to a thickness.

[0121] Next, a smoothing process used to smooth the surface of thesilicon film 658. In one embodiment, a H₂:HCl etching process is used.As illustrated in FIG. 61, the H₂:HCl etching process has an etchingprofile 673 which compensates the intended non-uniformity profile andhence, smoothes out the intended non-uniformity profile.

[0122] To smooth the silicon film 658 using the H₂:HCl etching process,the SOI substrate is placed in the smoothing chamber 508. Silicon film658 can be suitably treated by heating the handle wafer 600 to atemperature between 1000° C.-1300° C., preferably between 1050° C.-1200°C., and then exposing the thinned silicon film 658 to a gas mixturecomprising H₂ and HCl gases. In one exemplary embodiment, the handlewafer 600 is exposed to the gas mixture that comprises an H₂:HClmolecular concentration ratio between 10:1 and 1000:1. The handle wafer600 is heated and exposed to the H₂ and HCl gas mixture until thesilicon film 658 has a suitably smooth surface finish 664 is obtained asillustrated in FIG. 6J.

[0123] Additionally, the H₂:HCl concentration ratio can be varied duringsmoothing process in order to increase or decrease the removal rate.And, the H₂:HCl flow can be varied across the surface of the wafer(inner and outer locations) in order to manipulate the removal rateacross the surface of the wafer.

[0124] In another exemplary embodiment, the annealing process is used tosmooth the surface of the silicon film 658. In this embodiment, the SOIsubstrate (e.g., the handle wafer 602, the oxide layer 669, and thesilicon film 658) is placed in the annealing chamber 509. The annealingchamber 509 can be a conventional rapid thermal annealing processingchamber well known in the art. In another example, the annealing chamber509 can be a chamber similar to the apparatus 210 shown in FIG. 4. TheSOI substrate is heated up to a soak temperature, (an annealingtemperature), of about 1200° C. or higher. In one embodiment, a gas flowof a mixture including one or more gases such as H₂, N₂, He, Ar, or O₂is introduced into the annealing chamber while the SOI substrate isbeing heated up. In one embodiment, the flow rate of the gas mixture canbe greater than 1000 sccm for an annealing chamber of a 5-7 liter size.In one embodiment, the gas flow is across the SOI substrate across thesilicon film 658. In another example, an inert gas (e.g., Ar, Xe, He, orN₂) flow is introduced to the backside of the SOI substrate for fastcool down of the SOI substrate after annealing. In one embodiment, theSOI substrate is annealed in the presence of H₂ for about 10 seconds to60 seconds.

[0125] In one embodiment, the silicon film 658 has a surface roughnessless than 5 Å RMS and preferably less than 1 Å RMS after the smoothingprocess is completed. In one exemplary embodiment, about 1800 Å of thesilicon film 658 can be removed to generate a sufficiently smoothsurface. In another embodiment, the silicon film 658 thinned to lessthan 200 Å and preferably between 50-100 Å. Such a thin silicon film 658can be used to produce a compliant substrate for depositing a relaxeddefect free epitaxial silicon germanium film.

[0126] Next, if desired, an encapsulation film 666 is formed on thethinned and smoothened silicon film 658 as illustrated in FIG. 6K. Inone embodiment, the encapsulation film 666 is a high quality silicondioxide film formed using the loadlock apparatus 512 described above.

[0127] In another embodiment, additional silicon film(s) (not shown) canbe formed on the thinned and smoothened silicon film 658. In oneexemplary embodiment, the additional silicon film(s) are formed in thechamber 508 in which the silicon film 658 was smoothed. In this way, thetreated silicon 658 is not exposed to an oxidizing ambient or to otherpotential contaminants prior to the formation of the additional siliconfilms. This process is particularly useful for forming a protectingsilicon layer on the SOI substrate.

[0128] In one exemplary embodiment, the additional silicon film is asingle crystalline silicon film (epitaxial silicon) that can be formedby a chemical vapor deposition process in the chamber 508 using asilicon source gas, such as trichlorosilane or silane, and H₂ gas. Theadditional silicon film can be formed to any thickness desired and canbe formed to any conductivity type and density desired. In oneembodiment, the silicon film 666 has a p-type conductivity type and adopant density between 10¹⁵-10¹⁹ atoms/cm³ and is formed to a totalthickness between 1000 Å-50,000 Å. Alternatively, the silicon film canbe a silicon alloy such as silicon germanium.

[0129] A method and apparatus for treating a silicon or silicon alloysurface has been described. Although the present invention has beendescribed with respect to the treatment of a silicon film of an SOIsubstrate, and more particularly to a silicon film of an SOI substrateformed by an implant and cleave process, the present invention is not tobe limited to the exemplary embodiments. One skilled in the art willappreciate the ability to use the present invention to treat any siliconfilm and its surface to thin and smooth the silicon film. The siliconfilm treated using the exemplary embodiments has a uniform thicknessacross the silicon film, a smooth film surface across the silicon film,and a film thickness as thin as less than 200 Å.

In the claims
 1. A method of treating a silicon film comprising:providing a silicon film; treating said silicon film using a gas clusterion beam (GCIB) process; and annealing said silicon film using anannealing process to smooth at least one surface of said silicon film.2. The method of claim 1 further comprising: forming an encapsulationfilm over said silicon film to protect said silicon film after saidthinning and said smoothing.
 3. A method of treating a silicon filmcomprising: mapping an initial non-uniformity profile on said siliconsurface to obtain an initial non-uniformity mapping information;directing a gas cluster ion beam (GCIB) toward said silicon surfacewhile modulating said directing said GCIB according to said initialnon-uniformity mapping information to thin said silicon film to athickness; and smoothing at least one surface of said silicon film usingan annealing process.
 4. The method of claim 3 further comprising:forming an encapsulation film over said silicon film to protect saidsilicon film after said thinning and said smoothing.
 5. The method ofclaim 4 wherein said annealing process occurs in a rapid thermalannealing chamber.
 6. The method of claim 5 wherein said annealingprocess has a process temperature between 1100° C. and 130° C. and saidwherein said annealing process further comprises introducing a gas intosaid rapid thermal annealing processing chamber while heating up saidsilicon film.
 7. The method of claim 5 wherein said silicon film istreated in said rapid thermal annealing chamber for about 10 seconds to60 seconds.
 8. A substrate processing system comprising: a GCIB chamberhaving a first substrate holder to hold a substrate during a GCIBetching process, said substrate having a silicon film with a siliconsurface that has an initial non-uniformity profile; a rapid thermalannealing processing (RTP) chamber having a second substrate holder thatholds said substrate during a smoothing process, said smoothing processanneals said silicon film in a presence of a gas; a controller forcontrolling said GCIB chamber and said RTP chamber; a machine-readablemedium coupling to said controller, said machine-readable medium has amemory that stores a set of instructions for directing operations ofsaid GCIB etching process and said smoothing process; wherein said GCIBetching process thins said silicon film to a thickness and wherein saidsmoothing process smoothes out a surface of said silicon film after saidsilicon film is thinned with said GCIB etching process.
 9. The method ofclaim 8 further comprising: a loadlock apparatus wherein said controlleris further for controlling said loadlock apparatus and wherein said setof instructions are further for forming an encapsulation film over saidsilicon film to protect said silicon film after said smoothing process.10. The substrate processing system of claim 8 wherein said set ofinstructions are further for: storing an initial non-uniformity mappinginformation for said initial non-uniformity profile of said siliconsurface; directing a gas cluster ion beam (GCIB) toward said siliconsurface while modulating said directing said GCIB depending on saidinitial non-uniformity mapping information to thin said silicon film tosaid thickness; and smoothing said silicon surface in said RTP chamber.11. The substrate processing system of claim 8 wherein said set ofinstructions are further for maintaining a process temperature between1100° C. and 1300° C. for said RTP chamber and instructions forintroducing said gas into said RTP chamber while annealing said siliconfilm.
 12. The substrate processing system of claim 8 wherein said set ofinstructions are further for annealing said silicon film in said RTPchamber for about 10 seconds to 60 seconds.
 13. The substrate processingsystem of claim 8 wherein said gas is a mixture that includes one ormore of an argon (Ar) gas, a xenon (Xe) gas, a hydrogen (H₂) gas, anitrogen (N₂) gas, an oxygen (O₂) gas, or other gas.
 14. A method oftreating a silicon film comprising: providing a silicon film;incorporating an intended non-uniformity profile into a surface of saidsilicon film using a gas cluster ion beam (GCIB) process; and smoothingsaid surface using an etching process having an etching profile thatcompensates for said intended non-uniformity profile.
 15. The method ofclaim 14 further comprising: forming an encapsulation film over saidsilicon film to protect said silicon film after said smoothing.
 16. Amethod of treating a silicon film comprising: providing a silicon film;obtaining an initial mean thickness and initial non-uniformity profilefor said silicon film; thinning said silicon film to a thickness whileincorporating an intended non-uniformity profile into a surface of saidsilicon film; smoothing said surface using an etching process having anetching profile that compensates for said intended non-uniformityprofile.
 17. The method of claim 16 further comprising: forming anencapsulation film over said silicon film to protect said silicon filmafter said smoothing.
 18. A method of treating a silicon filmcomprising: mapping an initial non-uniformity profile on said siliconsurface to obtain an initial non-uniformity mapping information;creating an intended non-uniformity mapping information for an intendednon-uniformity profile to be incorporated into said silicon surface;directing a gas cluster ion beam (GCIB) toward said silicon surfacewhile modulating said directing said GCIB according to said initialnon-uniformity mapping information and said intended non-uniformitymapping information to thin said silicon film to a thickness and toincorporate said intended non-uniformity profile into said siliconsurface as said silicon film is being thinned; and smoothing saidsilicon surface using an etching process having an etching profile thatcompensates for said intended non-uniformity profile.
 19. The method ofclaim 18 further comprising: forming an encapsulation film over saidsilicon film to protect said silicon film after said smoothing.
 20. Themethod of claim 18 wherein said smoothing process is a H₂:HCl etchingprocess.
 21. The method of claim 20 wherein said H₂:HCl etching processoccurs in a single wafer deposition chamber.
 22. The method of claim 20wherein said H₂:HCl etching process has a process temperature between1000° C. and 1300° C. and wherein said H₂:HCl etching process furthercomprises exposing said silicon surface to a hydrochloric acid andhydrogen gas mixture.
 23. The method of claim 20 wherein the saidhydrochloric acid and hydrogen gas mixture has a molecular concentrationratio of HCl to H₂ of between 10:1 and 1000:1.
 24. A substrateprocessing system comprising: a GCIB chamber having a first substrateholder to hold a substrate during a GCIB etching process, said substratehaving a silicon film with a silicon surface that has an initialnon-uniformity profile; a smoothing chamber having a second substrateholder to hold said substrate during a smoothing process; a controllerfor controlling said GCIB chamber and said smoothing chamber; amachine-readable medium coupling to said controller, saidmachine-readable medium has a memory that stores a set of instructionsfor directing operations of said GCIB etching process and said smoothingprocess; wherein said GCIB etching process thins said silicon film andincorporates an intended non-uniformity profile into said silicon filmand wherein said smoothing process has an smoothing profile thatcompensates for said intended non-uniformity profile.
 25. The method ofclaim 24 wherein said smoothing process is a H₂:HCl etching process. 26.The method of claim 24 further comprising: a loadlock apparatus whereinsaid controller is further for controlling said loadlock apparatus andwherein said set of instructions are further for forming anencapsulation film over said silicon film to protect said silicon filmafter said smoothing process.
 27. The substrate processing system ofclaim 24 wherein said set of instructions are further for: storing aninitial non-uniformity mapping information for said initialnon-uniformity profile of said silicon surface; storing an intendednon-uniformity mapping information for said intended non-uniformityprofile; directing a gas cluster ion beam (GCIB) toward said siliconsurface while modulating said directing said GCIB depending on saidinitial non-uniformity mapping information and said intendednon-uniformity mapping information to thin said silicon film to athickness and to incorporate said intended non-uniformity profile intosaid silicon surface as said silicon film is being thinned; andsmoothing said silicon surface in said smoothing clamber.
 28. Thesubstrate processing system of claim 25 wherein said set of instructionsare further for operating said smoothing process at a processtemperature between 1000° C. and 1300° C.
 29. The substrate processingsystem of claim 25 wherein said set of instructions are further forintroducing a hydrochloric acid and hydrogen gas mixture into saidsmoothing chamber with a molecular concentration ratio of HCl to H₂ ofbetween 10:1 to 1000:1 during said smoothing process.
 30. A method oftreating a silicon film comprising: providing a silicon film; treatingsaid silicon film using a gas cluster ion beam (GCIB) process; andtreating said silicon film using an H₂:HCl etching process to smooth atleast one surface of said silicon film.
 31. The method of claim 30wherein said treating said silicon film using said GCIB process furthercomprises incorporating an intended non-uniformity profile into asurface of said silicon film and wherein said treating said silicon filmusing said H₂:HCl etching process smoothes out said intendednon-uniformity profile.
 32. The method of claim 31 further comprising:forming an encapsulation film over said silicon film to protect saidsilicon film after said treating said silicon film using said H₂:HCletching process.
 33. A method of treating a silicon film comprising:providing a silicon film; treating said silicon film to thin saidsilicon film and to incorporate an intended-non-uniformity profile intosaid silicon film; and smoothing said silicon film to smooth out saidintended non-uniformity profile.
 34. The method of claim 33 furthercomprising: incorporation said intended non-uniformity using a GCIBetching process.
 35. The method of claim 34 further comprising:smoothing out said intended non-uniformity using H₂:HCl etching process.36. The method of claim 33 further comprising: forming an encapsulationfilm over said silicon film to protect said silicon film after saidtreating said silicon film using said H₂:HCl etching process.